1. Field of the invention
The present invention relates to a flash device for use in photography and, more particularly, to a flash device which is mountable on a camera body and may change not only the direction of light emission, but also the angle of the cone of light manually to a desired angle of the cone of light, or automatically in response to the change of the focal length of the camera lens.
2. Description of the Prior Art
A flash device of the above described type has been proposed and is disclosed, for example, in U.S. Pat. Nos. 4,512,644, 4,423,940 and 4,462,666. According to U.S. Pat. No. 4,512,644, a lens is movably mounted in front of the light emitting element. The lens may move between a home position and an extended position so that the angle of the cone of light emitted by the light emitting element may be varied. The lens is moved by a motor automatically based on the focal length of the camera lens. If the focal length of the camera lens changes, such as in the case of a zoom lens, the lens mounted on the light emitting element moves accordingly so that the angle of the cone of light emitted by the flash device will be approximately the same as the photographic frame as defined by the camera lens.
Also, according to this reference, the flash head, in which the light emitting element is incorporated, can be pivoted to change the direction of emission of flash light. When the flash head is in the normal position, i.e., a direct flash mode position, the flash light is emitted parallel to the optical axis of the camera lens so as to illuminate the object directly by the flash light. When the flash head is pivoted to a bounce flash mode position, the flash light is emitted towards the ceiling to illuminate the object by the light which has bounced on the ceiling.
According to this reference, when the flash head is pivoted to the bounce flash mode position, the lens no more changes its position with respect to the change of the focal length, but it will be automatically moved to the home position so as to provide the widest angle of the cone of light. Then, when the flash head is pivoted back to the direct flash mode position, the lens will be moved again to the position based on the focal length of the mounted camera lens. The prior art flash devices have the problems given below.
By the pivotal movement of the flash head to the bounce flash mode, the lens is suddenly moved to the home position. When one is not aware of this, one may be surprised by such a sudden movement of lens FLE. Thus, one may drop the camera set. This will more likely happen when one tries to pivot the flash head to the bounce flash position by simultaneously grasping the front face, where the lens is mounted, and the rear face of the flash head with one's hand. In this case, if the lens was in the extended position before the pivot, the flash head may easily fall from one's hand when the lens suddenly moves to the home position during and/or after the pivot.
Also, when one tries to pivot back the flash head to the direct flash position by simultaneously grasping the front face and the rear face of the flash head with one's hand, the motor drive mechanism for driving the lens may be damaged. This can be explained as follows. When the flash head is pivoted back to the direct flash position, the motor drive mechanism automatically operates to push out the lens to a position determined by the focal length of the mounted camera lens. However, because one's hand is holding the lens, the motor might be burned out or the gears might be stripped.
Another problem may be encountered when the flash device is used in the bounce flash mode. When the flash head is pivoted towards the ceiling, for example 65.degree., and if a wide angle camera lens, such as a 28 mm lens, is mounted on the camera body, the light emitted from the flash device partly illuminates directly the object which is located within the photographing frame. This will result in an unbalanced lighting. The same can be said also of a flash device which has a fixed angle of the cone of light.
Yet another problem may arise when the position of the lens can be manually changed. If the camera lens mounted on the camera body is a wide angle lens, and if the angle of the cone of light emitted from the flash device, which is in the direct flash mode, is narrow as happens when the lens on the flash device is moved out, the object in the photographing frame may not be illuminated evenly by the flash light. This will also result in an unbalanced lighting.
A further problem arises when the flash device is used in combination with a ultra-wide lens, such as a 20 mm lens. If the flash device can emit light as wide as the area corresponding to a view that can be taken by a 28 mm lens, the use of the flash device in combination with such an ultra-wide lens (20 mm lens) will result in an unbalanced lighting.
The prior art is still seeking an improved flash device with the above problems being effectively removed.